Method and apparatus applying vibratory energy



N. MAROPIS 3,295,349

METHOD AND APPARATUS APPLYING VIBRATORY ENERGY Jan. 3, 1967 Filed Oct.4, 1965 INVENTOR.

86701:" L and 60/VOA Attorneys.

Patented Jan. 3, 1967 3,295,349 METHOD AND APPARATUS APPLYING VIBRATORYENERGY Nicholas Maropis, West Chester, Pa, assignor to AeroprojectsIncorporated, Chester, Pa., a corporation of Pennsylvania Filed Oct. 4,1965, Ser. No. 492,669 4 Claims. (Cl. 72-283) The present inventionrelates to a method and apparatus applying vibratory energy, and moreparticularly to a method and apparatus for applying vibratory energy inplug-drawing of articles including tubing.

Floating-plug drawing can be used on either discrete straight tubinglengths or long-length or coiled tubing (a draw bench being used for thefirst, and a draw block for the second). The application of vibratoryenergy in connection with such floating-plug drawing has been suggestedheretofore, in US. patent application Serial No. 321,041 filed November4, 1963, in the name of Charles A. Boyd, entitled, Apparatus and Methodfor Applying Vibratory Energy, now Patent No. 3,209,574. In thatapplication, it was proposed to use :a plug having a length equal to anintegral number of one-half wavelengths in the material of which it ismade at the frequency of operation.

It has now been found that considerably improved results are obtainedusing a plug having a physical length corresponding to an acousticlength of an odd integral number of one-quarter wavelengths of sound inthe material of which it is made at the frequency of operation.

Accordingly, it is an object of this invention to pro vide an improvedmethod and apparatus for drawing of tubing.

Another object of the invention is to provide an im proved system forplug drawing of tubing under vibratory energy application.

It is also an object of this invention to provide an improved floatingplug system for drawing of tubing under vibratory energy applicationwithout the necessity for joining the plug securely to a source ofvibratory energy.

A further object of this invention is to provide an improved method andapparatus for continuous drawing of tubing.

These and other objects of the invention are accomplished by providing aplug having a controlled acoustical geometry and by drawing with saidplug under the infiuence of a vibratorily activated die.

For the purpose of illustrating the invention, there is shown in thedrawings forms which are presently preferred, it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is an elevational view of apparatus embodying the presentinvention, partly in section and partly in diagrammatic form.

FIGURE 1A is an enlarged sectional view of a fragment of the apparatusillustrated in FIGURE 1.

Referring to the drawings in detail, wherein like numerals indicate likeelements, there is shown in FIGURE I 1 a vibratory tube drawingapparatus designated generally as 10.

The apparatus is in the nature of a draw bench (block) and includes adie 12 having an orifice 14. A floating plug 16 (see FIGURE 1A) extendsinto or through the orifice 14 and defines with the die 12 a restrictedpassageway through which the tube material 30 is drawn.

Die 12 is an element of a transducer-coupling system (designatedgenerally 'as 38), other elements of which are acoustical coupler 40 anda plurality of transducers designated a, 50b, 50c, and 50d (the last notshown).

System 38 is designed to operate at a given frequency, which ispreferably a resonant frequency. System 38 is preferably dimensioned tohave an over-all physical length equivalent to an acoustical length of awhole even number multiple of one-half wavelength in the material ofwhich it is made at the said frequency, so as to have, for efficientoperation, an antinode (loop) area of the vibration at thetube-contacting portion of the die.

Each of the transducers 50a, 50b, 50c, and 50d is preferably of theelectrostrictive-assembly type as shown. Reference is made to UnitedStates patent application Serial No. 456,900 filed May 11, 1965, in thenames of James Byron Jones and Nicholas Maropis and entitled, TransducerAssembly, for details concerning construction and advantages of atransducer such :as transducer 50a. The transducers 50b, 50c, and 50dare constructed in the same manner as transducer 50a.

While the above indicated electrostrictive transducer construction ispreferred for purposes of the present invention, it will be appreciatedby those skilled in the art that other known types of transducers may besubstituted. For example, other types of electrostrictive,piezoelectric, or magnet-ostrictive transducers may be utilized.

The transducers StPa-b-c-d are connected to a power supply (not shown)suitable for powering them at the desired frequency. In the case of thisembodiment, that frequency is 28,000 cycles per second (28 kc.),inasmuch as each of the transducers Stla-b-c-d is constructed to operateat that nominal frequency. Such power supply equipment is well known tothe art.

The aforesaid power supply system, in a typical example, is capable ofproducing electrical signals in the range of between about cycles persecond and about 300,000 cycles per second. This frequency range issuitable for purposes of the present invention, including as it doesfrequencies in both the audible range (such as up to about 15,000 cyclesper second) and the ultrasonic range (generally above about 15,000cycles per second). A preferred frequency would be in the range of fromabout 3,000 to about 50,000 cycles per second, with the optimum beingbetween about 14,000 to about 35,000 cycles per second. Normally, :afrequency is chosen which will provide a suitable size of apparatus fora given application or set of applications, with the ultrasonic rangehaving the further advantage of inaudibility for operator comfort.

Thus, transducer-coupling system 38 may be constructed to operate at28,000 cycles per second, for example.

As is well known to the art, the electrical frequency of the alternatingcurrent power supply (such as 60 cycles per second) is changed to matchthe mechanical or elastic vibratory frequency of thetransd.ucers.(28,000 cycles per second in this example, as aforesaid).

It is to be noted that the source of high frequency alternating currentmay be of the solid state type (generally more suitable for relativelylow power requirements), the vacuum tube type (generally for low orintermediate power requirements), or the motor alternator type withsuitable frequency control (particularly appropriate for applicationsrequiring relatively large amounts of power).

The die 12 has, for purposes of ease of attachment to acoustical coupler40, an axially extending portion 42 (see FIGURE 1A) to whose outersurface one end of coupler 40 is secured by means of cooperatingthreads. The other end of coupler 40 which is remote from the die (saidend having four projections in this embodiment) is fixedly secured tothe transducers 50a-b-c-d. That is, one end projection of coupler 40 isjoined to transducer 50a, the second end projection is joined totransducer 50b, the third to transducer 500, and the fourth totransducer 50d, preferably by brazing or some other type ofmetallurgical joint or as described (for the transducer-assembly of thisembodiment) in the above-identified application Serial No. 456,900.

Acoustical coupler 40 is essentially a mechanical transformer and is ofcontoured construction for purposes including the increasing of theamplitude of vibration. Reference is made to United States Patent No.3,148,293 issued September 8, 1964, in the names of James Byron Jones etal., entitled, Vibratory Device for Delivering Vibratory Energy at HighPower, for details concerning construction and advantages of a couplersuch as coupler 40.

The horn-type construction of system 38 is particularly suitable forapplication of relatively high levels of vibratory energy at a givenfrequency, and for avoiding undesirable modes of vibration in connectionwith both .die 12 is supported by a force-insensitive mount 52.

Such force-insentitive mount 52 may comprise a sleeve,

.one-half-wavelength long at the operating frequency and made from steelor other low hysteresis material such as nickel, aluminum bronze,beryllium-copper, or Monel. One end of the sleeve 52 is metallurgicallyjoined to the coupler 40, preferably at an antinode or loop region ofthe vibration on the cylindrical portion of the latter, and the otherend of the sleeve 52 is free from attachment. Sleeve 52 is provided witha radially outwardly extending flange 58 located one-quarter wavelengthfrom its free end, and a true acoustical node will develop at the regionof flange 58. Reference is made to United States Patents Nos. 2,891,178,2,891,179, and 2,891,180 each of which issued in the name of William C.Elmore and is entitled, Support for Vibratory Devices.

Flange 58 is removably secured to a support 60 as by a clamping ring 61and suitable bolts. Support 60 is rigidly secured to the draw bench 36.

The mount 52 in the drawing comprises a conical tubular member (a formwhich is not necessarily preferred').

' Acoustical coupler 40 and die 12, like support mount 52, arepreferably made from K-Monel or other material having low hysteresis,good thermal conductivity, and high acoustical transmission efiiciencyeven when strained as much as 0.00l-inch per inch, for example,including such materials as aluminum-bronze or beryllium-copper. Thematerials named are non-magnetic and are known to the art for theirrelatively good acoustical power handling qualities. However, fordrawing purposes the die 12 may be made of other materials, such asthose chosen principally for suitability for the drawing operation perse rather than for their acoustical properties, provided that suchchange in material for the die is taken into consideration in connectionwith the design of the system for operation at a resonant frequency, ashas been indicated to be preferable for purposes of the presentinvention.

In accordance with the present invention, there is provided afree-floating plug 16 having a forming end 18 and a free-floating end20. Plug 16 may comprise a single member or ends 18 and 20 may bemanufactured as separate members which may be fixedly connected (as by ametallurgical joint such as a brazed joint) or removably connected (asby cooperating threads).

It is to be noted that (unlike coupler 40, die 12, and mount 52, andunlike the floating plug in the above-identified application 321,041)the plug 16 is preferably made of a non-acoustically-optimum material.Thus, it may be and preferably is made of a material such as tungstencarbide, which is not only suitable for the drawing operation per se butis also particularly suitable for purposes of the present invention.

Thus, for purposes of appropriate acoustical behavior of the plug of thepresent invention, it is not desired to transmit acoustical energy fromthe end 18 of the plug 16 to the tube 30 and/or the die 12. Rather, itis desired that the plug 16 behave as an essentially noncompliantelement acoustically in the region of actual material reduction (i.e.,at the region of the plug 16 adjacent to the die 12). That region on theplug 16 will then present a high impedance to the transmission ofvibratory motion in an axial direction; it will be an axial node, so tospeak.

Thus, while I do not wish to be bound by any explanation or theory as tothe mechanism of operation of the present invention, it appears that thefree end 20 of plug 16 (when dimensioned as aforesaid) may behave as aloop or antinode, both by virtue of its freedom and its relationship tothe nodal region from which vibration is transmitted back to it via thePoissons ratio effect, which effect causes end 20 to vibrate in phasewith the vibration of the die 12. However, the primary concern of thepresent invention is in providing the aforesaid acousticallynon-compliant behavior of the end 18 of the plug 16.

The aforesaid quarter-wave dimensioning of the plug 16 and itsacoustically non-compliant behavior appears to serve to concentrate thevibratory energy in the area of material reduction where it is mostuseful, thus enhancing the tube drawing process without the directaddition of vibratory energy through the plug (such as the prior art hascontemplated).

In operation, as shown in FIGURES 1 and 1A, the forming end 18 of theplug 16 extends into and through the orifice 14 and defines with the die12 a restricted passageway through which the tube material 30 is drawn.

Plug 16 (like transducer-coupling system 38) is designed to operate at agiven frequency, which as aforesaid is preferably a resonant frequency,namely, the design frequency of system 38 (such as the 28,000 cycles persecond :above mentioned, for example). However, plug 16 is preferablydimensioned to have an over-all physical length equivalent to anacoustical length of an odd in tegral number of one-quarter wavelengthsof sound in the material of which it is made at the said frequency. Thisis so that it will vibrate in the direction of the vibration system 38,and so as to have for efficient operation an acoustical node area of thevibration at the tube-contacting portion of the forming end 18 of plug16, namely, juxtaposed to the die orifice 14. Also, in this embodiment,plug 16 will have each of its two ends 18 and 20 operating out of phasewith one another, and end 18 being acoustically non-compliant withrespect to longitudinal vibrations of the die 12.

It is to be noted that the shape of forming end 18 of die 12 may involvea slight adjustment in the aforesaid acoustical dimensioningrequirements above indicated for plug 16, but this is within the skillof the art.

As is well known, the velocity of compressional waves in a medium variesaccording to the medium; the appropriate length of plug 16 may be foundby use of the well known equation (wavelength=velocity/frequency)showing the relation among frequency, velocity, and wavelength of sound.Thus, if the plug 16 is to be made of tungsten carbide (such as atungsten carbide comprising 87% tungsten and 13% cobalt), the pertinentcharacteristics of the tungsten carbide are ascertained (varioustungsten carbides may have various values for Youngs modulus and densitywhich will result in various velocities of sound), and the one-quarterwavelength dimension is calculated.

In this embodiment, the tungsten carbide had a modulus of 80 10 p.s.i.(=53.4 10 dynes/cm. a density of 14.15 gm./c-m. and a sound velocity ofabout 6150 meters/ sec. Therefore, a plug 16 having a length of one (1)one-quarter wavelength would have a physical length of 2.16 inchesaccording to the equation for operation at 28 kc. With a smallcorrection for the tapered end 18, the plug length could be about 2.25inches for operation at that nominal frequency.-

It will be appreciated that, as in conventional drawing, various dieangles and plug-end angles may be used. As yet these angles have notbeen shown to be critical as to use with the present invention, exceptas may concern the reduction desired to be obtained in a particularapplication.

In operation, tubing 30 is telescoped over the plug 16 (usually aftertubing pre-treatment such as pickling, cleaning, and lubrication,although tubing pre-treatment may be minimized or eliminated in someinstances and with some materials when the present invention is used).The plug 16 is so arranged that the plug forming end 18 floats in theproper position in the die orifice 14. The tubing 30, in accordance withstandard practice, may be pointed, i.e., provided with a reduced outsidediameter end portion, which may be accomplished in a variety of waysincluding swaging. Such reduced end portion is fed in the direction ofarrow 90 through the die orifice 14. The jaws 64a and 64b of a pullingdevice 62 are clamped to the reduced end portion 32 of the tubing 30.Pulling device 62 is movably mounted on drawbench 36 for pullin thetubing 30 through the passageway defined by die 12 and forming end 18 ofplug 16. The pulling device 62 is first actuated in the direction ofarrow 90 to seat the forming end 18. That is, the tubing 30 is pulled inthe direction of arrow 90 until the tubing 30 is locked between the dieorifice 14 and the outer peripheral surface of the forming end 18 ofplug 16.

The tubing 30 can be translated by the pulling means for a shortdistance, so that the plug will seat properly and drawing can be readilyaccomplished. However, the invention is not limited to any particularsequence of steps in pointing the tubing and/or seating the plug,although certain sequences may be far more favorable than others. As isreadily evident, various lengths of tubing may be accommodated inaccordance with the present invention, including very long lengths, asfor example in continuous drawing.

After the forming end 18 of plug 16 is properly seated and positioned,and vibratory energy is applied to the system 38 including the die 12(and by reason of its acoustical geometry to the plug 16), the pullingdevice 62 will move the jaws 64a and 64b in the direction of arrow 90. Awide variety of devices may, of course, be utilized to pull the jaws 64aand 64b, such as a hydraulic cylinder, a cable windup device, etc. Itwill be appreciated that the jaws 64a and 64b will be provided withmeans for selectively opening and closing the same, so that the reducedend portion of the tubing 30 may be inserted and gripped therebetween.

It will be appreciated that the power input to the transducers may bevaried according to the operating conditions utilized, including thematerial being drawn and the conditions of draw (such as the reductionto be achieved, the drawing speed, and the drawing tension), and alsoaccording to the transducer-coupling system and plug employed.

The position of the forming end 18 of plug 16 relative to the die 12 anddie orifice 14 is a determinant of the depth of draw, and afree-floating plug such as plug 16 is more susceptible to dislodgement(under either conventional or vibratory drawing conditions) than is abacksupported plug, for example.

The amount of power supplied and transmitted to the die area should notbe suflicient to dislodge the forming end 18 of plug 16 from itslocation specified for drawing purposes. On the other hand, the powershould be suflicient to accomplish the given reduction under a given setof operating conditions for a given material.

As is well known to those skilled in the art, power output (to the work)of acoustical vibration devices is not readily ascertainable directly,and indirect determination thereof often involves the use of liquids andother aspects not suitable for ready adjustment to differing industrialapplications. Moreover, permissible power input is variable according tothe transducer utilized and the acoustical coupler geometries andmaterials used, as well as such factors as the efliciencies of jointsbetween the various members of the transducer-coupling system. Forexample, a magneto-strictive transducer is far more rugged andtrouble-free than the ceramic transducers which have been in commercialuse, but it has a lesser efiiciency in converting electrical power intomechanical vibration. Also, steel is a more readily machinable andjoinable coupler material than Monel or beryllium-copper, but it has alesser acoustical transmission efficiency. The implications are obviousfor differing amounts of acoustic power (expressed in electrical wattsoutput from the power supply or input to the transducer) used withvarious equipments, even without taking a given drawing operation intoconsideration.

A lubricant may be applied to the inner and/ or outer surfaces of thetubing 30 by means well known in the art. Such lubricants andlubrication are well known to the art, and they do not form a part ofthe present invention, except to the extent that the present invention(with some materials and undersome conditions of draw) enableselimination or minimization of lubrication, including a lessening ofcriticality concerning the use of a special lubricant for a givenmaterial.

For example, in one example of utilization of the present invention,successful drawing was obtained of an ironnickel alloy tubing whichcould not be successfully drawn without vibratory energy as provided bythe present inlention. However, a careful choice of tube lubricant wasnecessary if tube failures were to be reproducibly avoided.

In another example, also using the tungsten carbide plug with the abovesingle one-quarter wavelength dimensions, successful drawing at 75 feetper minute was obtained (at a 40% area reduction) of copper tubinghaving a diameter of 0.093-inch and a wall thickness of 0.0062-inchbefore the vibratory drawing. This reduction could not be made withoutthe present invention, not even with the invention of the aforementionedSerial No. 321,041, now Patent No. 3,209,574.

US. patent application Serial No. 289,559 filed June 21, 1963, in thenames of Charles A. Boyd et al., entitled, Vibratory Energy Method andApparatus, now Patent No. 3,209,572, has been found useful in connectionwith initial seating of the plug of the present invention and subsequentapproach to the ultimately used vibratory drawing conditions. Thus,drawing may be initiated at a very low electrical input to thetransducer to permit plug seating (drawing speed 37.5 feet per minute)and then power may be increased to the operating'level as drawing speedis increased to the above-indicated 75 feet per minute for theapplication specified.

Other advantages of the present invention in some applications mayinclude the providing of optimum material plasticity with resultantoptimum drawing tension reduction, decreased chattering tendencies,increased drawing speed, and greater material reductions per pass thanare obtainable in conventional free-floating plug drawing.

In view of the free-floating end 20 of plug 16s being acoustically freeat its outer end (i.e., delivering no vibratory energy in view of theacoustical impedance mismatch with air), the nodal region(s) at oddwhole number multiples of one-quarter-wavelength from said end 20s outerend are true acoustical nodes, which is a condition nonaachievable as apractical matter, so far as is known, in a transducer-coupling systemunder power delivery conditions.

For efiicient operation, the pulling device 62 (including the jaws 64aand 64b) should not resonate in any mode at the frequency of operation.

Although the invention is shown and described in connection with thedrawing of tubes, it is to be understood that the invention isapplicable generally to the drawing of elongated articles having wallstructure formed at least partly about a longitudinal axis thereof.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing description as indicating the scope of theinvention.

I claim:

1. Vibratory tube drawing apparatus comprising a die having an orificetherein, a vibratory generator coupled to said die, means on one side ofsaid die for pulling tubing in an axial direction through said orifice,a free-floating plug partially disposed in said orifice, said plughaving a physical length corresponding to an acoustical length of an oddintegral number of one-quarter wavelengths of sound in the material ofwhich it is made at the frequency of said vibratory generator, said plughaving one end thereof in said orifice and a second end thereof on theside of said die opposite from said pulling means, said plug beingacoustically non-compliant at said one end.

2. Apparatus for drawing elongated articles wherein said articles havewall structure formed at least partly about a longitudinal axis thereof,said apparatus comprising a die having an orifice therein, afree-floating plug extending at least partially into said orifice fromone side of said die and defining with said die a restricted passagewayfor an article to be drawn, means associated with said die on the sidethereof opposite said plug for pulling an article through saidpassageway, a vibratory generator including a transducer and anacoustical coupler coupled to said die, said transducer and couplerbeing arranged so as to vibrate in an axial direction so that avibratory antinode occurs in said die, said plug having a length equalto an odd integral number of one-quarter Wavelengths of sound in thematerial of which it is made at the frequency of said vibratorygenerator, the portion of said plug which cooperates with said die toform said passageway being a vibratory node on said plug.

3. A method of drawing tubes comprising the steps of providing anacoustically non-compliant free-floating plug, telescoping a tube aroundthe plug, feeding a reduced diameter portion of said tube to a die,seating a vibratory node on said plug against the portion of said tubejuxtaposed to the orifice of said die, coupling vibratory energy to saiddie, inducing vibrations in said plug out of phase with vibrations ofsaid die, and pulling said reduced diameter portion of said tube in anaxial direction away from said die to reduce the cross sectional area ofsaid tube as it passes through said die.

4. The method of claim 3 wherein the step of providing a plug includesproviding a plug having a length equal to an odd integral number ofone-quarter wavelengths of sound in the material of which it is made atthe frequency of the vibratory energy applied to said die.

References Cited by the Examiner UNITED STATES PATENTS 2,891,180 6/1959Elmore 31026 3,002,614 10/1961 Jones 72253 3,203,215 8/1965 Jones 72-2533,209,574 10/1965 Boyd 72-283 FOREIGN PATENTS 955,943 1/1957 Germany.

CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner.

1. VIBRATORY TUBE DRAWING APPARATUS COMPRISING A DIE HAVING AN ORIFICETHEREIN, A VIBRATORY GENERATOR COUPLED TO SAID DIE, MEANS ON ONE SIDE OFSAID DIE FOR PULLING TUBING IN AN AXIAL DIRECTION THROUGH SAID ORIFICE,A FREE-FLOATING PLUG PARTIALLY DISPOSED IN SAID ORIFICE, SAID PLUGHAVING A PHYSICAL LENGTH CORRESPONDING TO AN ACOUSTICAL LENGTH OF AN ODDINTEGRAL NUMBER OF ONE-QUARTER WAVELENGTHS OF SOUND IN THE MATERIAL OFWHICH IT IS MADE AT THE FREQUENCY OF SAID VIBRATORY GENERATOR, SAID PLUGHAVING ONE END THEREOF IN SAID ORIFICE AND A SECOND END THEREOF ON THESIDE OF SAID DIE OPPOSITE FROM SAID PULLING MEANS, SAID PLUG BEINGACOUSTICALLY NON-COMPLIANT AT SAID ONE END.